1. Field of the Invention
The present invention relates to an apparatus for bonding substrates together, and more particularly, to a substrate bonding apparatus for a liquid crystal display (LCD) device panel.
2. Discussion of the Related Art
As demand for displaying various types of visual information increases, different types of display devices, such as LCD devices, plasma display panel (PDP) devices, electro-luminescent display (ELD) devices, and vacuum fluorescent display (VFD) devices, are being developed. Among these different types of display devices, the LCD devices are commonly used in portable display devices and are used to replace cathode ray tube (CRT) devices because of their excellent image quality, light weight, thin profile, and low power consumption. In addition to the portable type LCD device, such as monitors of notebook computers, LCD devices are used in television systems for receiving and displaying broadcasting signals, and as monitors of desktop computers. However, despite the various technical advantages for using LCD devices as display devices, LCD devices lack high image characteristics, such as high definition and high luminance, and are difficult to implement in large-sized display screens.
The LCD devices are commonly fabricated using a liquid crystal injection process in which sealant is patterned upon one of upper and lower substrates to form an injection hole, and the upper and lower substrates are bonded together within a vacuum chamber. Then, liquid crystal material is injected through the injection hole into a region between the upper and lower substrates. Alternatively, a liquid crystal dispensing process is used, as suggested in Japanese Laid Open Patent Nos. 2000-284295 and 2001-005405. Accordingly, one of an upper and lower substrate has the liquid crystal material dispensed thereupon, and another of the upper and lower substrates is positioned adjacent to the substrate having the liquid crystal material, and they are bonded together under vacuum pressure.
FIGS. 1 and 2 are cross sectional views of a substrate bonding apparatus for fabricating an LCD panel according to the related art. In FIGS. 1 and 2, a substrate bonding apparatus includes a frame 10 forming an outer appearance, an upper stage 21 disposed in an upper chamber part 31, a lower stage 22 disposed in a lower chamber part 32, and a liquid crystal material dispenser 30. In addition, although not specifically shown, the substrate bonding apparatus includes a sealant dispenser, a chamber moving device, and a stage moving device. The sealant dispenser (not shown) and the liquid crystal dispenser 30 are mounted at a side of a position the frame 10.
As shown in FIG. 2, the upper chamber part 31 and the lower chamber part 32 are joinable together. The chamber moving device includes a first driving motor 40 and a second driving motor 50. The first driving motor 40 that selectively moves the lower chamber unit 32 to a position S2 during a bonding process, or to a position S1 during dispensing of sealant from the sealant dispenser (not shown) and dispensing of liquid crystal material from the liquid crystal material dispenser 30. The second driving motor 50 selectively moves the upper stage 21 along vertical directions to the upper chamber part 31.
A process for fabricating an LCD device using the substrate bonding apparatus of FIGS. 1 and 2 according to the related art includes a loading process, as shown in FIG. 1, including attaching a first substrate 51 onto the upper stage 21 in a loaded state, and attaching a second substrate 52 onto the lower stage 22 in a loaded state. Next, the lower chamber part 32 having the lower stage 22 is moved to the position S1 by the first driving motor 40. Then, sealant material and liquid crystal material are dispensed onto the second substrate 52 by the sealant dispenser (not shown) and the liquid crystal material dispenser 30, respectively.
Next, as shown in FIG. 2, the second substrate 52 is moved to the position S2 by the first driving motor 40 for positioning the first and second substrates 51 and 52 together. Then, a joining process for joining the upper and lower chamber parts 31 and 32 together is performed by the first driving motor 40, thereby enclosing a space between the joined upper and lower chamber parts 31 and 32. Next, a pressure within the enclosed space is reduced to a vacuum state by a vacuum system (not shown). Under the vacuum state, the upper stage 21 is moved down by the second driving motor 50 so that a space between the first substrate 51 and the second substrate 52 is reduced. Accordingly, the first and second substrates 51 and 52 make contact with each other, and are pressed together by further movement of the second driving motor 50. Then, the upper stage 21 is withdrawn from the lower stage 22 such that the bonded first and second substrates 51 and 52 remain on the lower stage 22. Next, the pressure within the joined upper and lower chamber parts 31 and 32 is increased to an atmospheric pressure, and the joined upper and lower chamber parts 31 and 32 are separated. Then, the bonded first and second substrates 51 and 52 are removed from the lower stage, thereby completing the process for fabricating an LCD device.
However, the process for fabricating the LCD device has the following disadvantages. First, since the bonding apparatus requires dispensing of the sealant material and the liquid crystal material onto one of the substrates and bonding of the substrates together, the overall size of the substrate bonding apparatus must be large. Accordingly, as sizes of substrates increases, an overall size of the bonding apparatus must also increase. Thus, the bonding apparatus has a maximum limit both for the size of substrates that may be bonded together, and for a physical limitation of the bonding apparatus itself.
Second, since the lower chamber part 32 must be repeatedly moved between the first second positions S1 and S2 during each bonding process, alignment between the upper and lower stages 21 and 22, and subsequently, between the first and second substrates 51 and 52 may become inaccurate.
Third, since the upper and lower chamber parts 31 and 32 are repeatedly joined together and separated apart, sealing of the upper and lower chamber parts 31 and 32 may deteriorate. Accordingly, air and foreign matter may be allowed to enter into an interior portion of the joined upper and lower chamber parts 31 and 32. Thus, defective bonding of the substrates will occur.
Fourth, the substrate bonding apparatus according to the related art requires a relatively large space for performing bonding of the substrates. Thus, a facility to house the frame of the substrate bonding apparatus requires an unnecessarily large amount of unusable floor space, thereby reducing space efficiency and increasing manufacturing costs. In addition, the substrate bonding apparatus requires a significant amount of process time to produce the bonded substrates, and power consumption for generating the vacuum pressure within the joined upper and lower chamber parts is relatively large.